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[APD] Metal Halide lights on timers

Message: 4
Date: Mon, 12 Jan 2004 08:50:20 +1100
From: Andrew Mitchell <andrewm at cse_unsw.edu.au>
Subject: [APD] Metal Halide lights on timers
To: aquatic-plants at actwin_com

Hi all,

I have 4 150w metal halide lights (and 2 double 4ft flourescents) on
timers on my 300+g tank.

I have been keeping these for over a year now on those cheap $5-10
timers from the local hardware/department store. (I use 2 timers, each
for half the load)

About a month ago one of them failed. I replaced it. 3 Days later the
new one failed. I replaced it with a different brand. That lasted about
another 2-3 days. Each failure was the case that I got up in the 
and the light was still on, despite all indications on the timer itself
that the light should be off... the relay in the timer appears to have
welded shut!
Has anyone else had a similar problem or have any suggestions?
The best thing I can think of is to try 3 $5 timers (one on each MH and
one on the flouros) to see which is causing the problem. But then what?

Hi Andrew,
       With reference to the mail above,I'd suggest to use heavy duty relay contacter.
This is what I've in planned for my MH setup,6500K Osram . Currently using 4x36W PLL,6000K Osram. Though My timer has not given me any trouble so far, still I would like to plan for the future Setup & design my Electrical console.
       In the figure below the TIMER is used to switch on a STEP DOWN TRANSFORMER ,which  trigger a Heavy Duty Relay CONTACTER which in turn switches ON the LOAD.
                       Timer          Step Down          Heavy Duty           To High 
                       OUT           Transformer      Relay contacter          LOAD 
                  |                  |                                               |
                  |    ______    |                            ________     |
        LIVE-------|         _|---            (8)  | (8)---------||          _ ||----|
                      |        \_|--Live--------(8)  | (8)        ||          \_ ||------------>Live   
                      |           |               (8)  | (8)         ||             ||                         MH Ballast
NEUTRAL-------|______|--Neu--------(8)  | (8)---------||_______||------------->Neutral

                   |               |                               ^IN    OUT^   |

                   |               |                                                  |
                   |_________|_____Neutral_________________ |
1. TIMER - Any suitable Real Clock / Cyclic timer.
2. Heavy Duty Relay CONCTACTER - This has to be chosen appropriately w.r.t  the LOAD. (Eg:U pick up a Contacter with operating Voltage24V .U can get a 2-pole,4-pole,6-pole contacter, choose as per the number of equipments you'd want to switch U can either use the contacter to switch the Live wire & bypass the relay for Neutral between the equipments OR use a both the L & N thrrough the Relay )(My Plan:Use a 6-Pole Contacter with 12V operating voltage)
3. STEP DOWN TRANSFORMER - The transformer should be able to energize the CONTACTER. (Eg: the transformer should be able to drive the Contacter (CAUTIO
N: Overdriving the Contacter can reduce its life).(My plan: Get a Torodial Transformer,low on heat & losses, made to order 12V, ampere as per the contacter requirement)
4. LOAD - U can then use a MH, PLL,CFL or Regular tube lights.
    This way one does not need to invest on a high load timer & since the LOAD in on the CONTACTER the the life expectancy of the timer is drastically improved.
Hope this helps.
Thanks & Regards
Deepak Brid

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